1. Field of the Invention
The present invention generally relates to a mechanism for producing minute movement of a head of a disk device and, more particularly, to a mechanism for causing a minute movement of a head of a disk device in the vicinity of a leading end of a piezoelectric element by utilizing shear deformation of the piezoelectric element.
2. Description of the Related Art
In recent years, the processing precision of information devices has advanced. Thus, there is a demand for actuators required to control micro-distance movement of constituent components of the information devices. That is, actuators capable of controlling micro-distance movement of a head or the like are needed in the fields of, for example, devices for correction of focal points of optical systems and control of tilt angles of optical components thereof, printing devices for printers, and head actuators of magnetic disk devices.
Among such information devices, a magnetic disk device a primary multimedia device, the scale of the market of which has sharply increased. Multimedia devices deal with mass image and audio data at high speeds. Thus, there is a need for development of a device having higher storage capacity. Generally, a magnetic disk mass storage device realized by increasing the storage capacity per disk.
However, it is indispensable for realizing a magnetic disk medium having a high recording density to increase the number of tracks per inch (TPI), that is, to reduce the width of each track. Further, when the storage density of a magnetic disk is significantly increased, the track pitch abruptly decreases. Thus, there is a technical problem as to how the positioning of a head element for reading data from and writing data to a recording track is accurately performed. Hence, there has been put to practical use a head actuator, which is caused by a motor called a xe2x80x9cVCMxe2x80x9d to perform a rocking motion and has a mechanism capable of causing minute movement of a head independently of a driving operation by the VCM. This mechanism for producing a minute movement of a head must be miniaturized.
A first object of the present invention is to provide a mechanism for producing a minute movement of a head, which is suitable for accessing disks in a narrow space between stacked disks, in a head actuator of a magnetic disk unit having such a mechanism.
A second object of the present invention is to reduce the cost of a disk device by simplifying the wiring for driving a mechanism for producing a minute movement of a head and wiring for connecting a head suspension to the ground.
To achieve the foregoing objects, according to an aspect of the present invention, there is provided a mechanism (hereunder sometimes referred to as a first mechanism of the present invention) for producing a minute movement of a head, provided between a base portion of a head suspension having the head at an end portion thereof and an end portion of a carriage arm swinging around a rotation shaft in a rocking type head actuator. This mechanism comprises a stationary member, which is fixed to the end portion of the carriage arm, a moving member, which is attached to the base portion of the head suspension, and a displacing member, which is interposed between a free-end-side predetermined-area surface of the stationary member and a free-end-side predetermined-area surface of the moving member opposed to the stationary member, having a top surface to be displaced with respect to a bottom surface thereof by applying a voltage in a direction of the thickness thereof. This displacing member is placed at a side opposite to a recording medium to be accessed, with respect to an attaching surface of the stationary member, which is attached to the end portion of the carriage arm, and an attaching surface of the moving member, to which the base portion of the head suspension is attached.
In the first mechanism of the present invention, a space formed between the free-end-side predetermined-area surface of the stationary member and the free-end-side predetermined-area surface of the moving member by folding a part adjoining the attaching surface of the stationary member, which is attached to the end portion of the carriage arm, like a crank, to a side of the recording medium. The displacing member is accommodated in this space.
Further, in the first mechanism of the present invention, a space formed between the free-end-side predetermined-area surface of the stationary member and the free-end-side predetermined-area surface of the moving member by folding a part adjoining the attaching surface of the moving member, which is attached to the end portion of the carriage arm, like a crank, to a side of the recording medium. The displacing member is accommodated in this space.
Furthermore, the first mechanism of the present invention has the following characteristic features:
(1) Application of the voltage to the displacing member is performed by sheet-like electrode members provided on the top and bottom surfaces of the displacing member. Moreover, insulating members are interposed between the electrode member and the stationary member and between the electrode member and the moving member. Each of the electrode members has a connecting terminal portion connected to a lead wire that is connected to a power supply.
(2) The carriage arm is connected to the ground. The stationary member is constituted by an electrical conductor and fixed to the end portion of the carriage arm in such a manner as to electrically conduct. An insulating layer, a conductive layer, and an electrode member having a connecting terminal portion connected to a lead wire, which is connected to a power supply, are provided between the stationary member and the displacing member so that the conductive layer is provided at the side of the displacing member. The moving member is constituted by an electrical conductor and is attached to the base portion of the head suspension in such a way as to electrically conduct. The moving member is connected to the stationary member by an electrical conductor.
(3) The carriage arm is connected to the ground. The stationary member is constituted by an electrical conductor and fixed to the end portion of the carriage arm in such a manner as to electrically conduct. An insulating layer, a conductive layer, and an electrode member having a connecting terminal portion connected to a lead wire that is connected to a power supply, are provided between the stationary member and the displacing member so that the conductive layer is provided at the side of the displacing member. The moving member is constituted by an electrical conductor and is attached to the base portion of the head suspension in such a way as to electrically conduct, and is overlaid directly on the displacing member. The moving member is connected to the stationary member by an electrical conductor.
The conductor is also used as a part of the head suspension.
(4) The moving member is constituted by an electrical conductor. An electrode member consisting of an insulating layer and an electrical conductive layer is fixed to a base-portion-side part of a surface of the moving member, which is opposite to the displacing member. The electrode member has a wire connecting portion connected to external wiring. The conductive layer of the electrode member is connected to the moving member by an electrical conductor. The electrical conductor can be a conductive adhesive agent.
(5) The carriage arm is connected to the ground. An electrode member consisting of an insulating layer, an electrical conductive layer, and a connecting terminal portion to be connected to an external lead wire is provided so that the conductive layer is in contact with a moving-member-side surface of the displacing member. A stationary-member-side surface of the displacing member is electrically connected to the carriage arm through the stationary member constituted by an electrical conductor. The moving member, to which the head suspension is attached, is constituted by an electrical conductor and connected to the stationary member by an electrical conductor.
(6) The carriage arm is connected to the ground. An electrode member consisting of an insulating layer, an electrical conductive layer, and a connecting terminal portion to be connected to an external lead wire is provided so that the conductive layer is in contact with a moving-member-side surface of the displacing member. A stationary-member-side surface of the displacing member is electrically connected to the carriage arm through the stationary member constituted by an electrical conductor. The moving member is constituted by an electrical conductor, is connected to the base portion of the head suspension in such a way as to electrically conduct, and is overlaid directly on the displacing member. The head suspension is connected to the stationary member by an electrical conductor.
Further, the mechanism of the configurations (1) to (6) may have the following characteristic features:
(7) The electrode member is constituted by stacking a stainless-steel thin plate, a polyimide layer, and a copper foil in this order.
(8) The electrode member is constituted by a flexible printed circuit board. The connection of the printed circuit board, the piezoelectric element, the moving member, and the stationary member is performed by gluing.
(9) The wire connecting portion of the electrode member is folded in such a way as to fit along a side surface of the carriage arm.
(10) The moving member has a hinge portion for increasing a moving range of the head suspension. Moreover, the electrode member has a notch formed in accordance with a shape of a hinge of the moving member having the hinge.
Incidentally, in any of the mechanisms of the aforementioned configurations, a surface, on which the moving member is mounted, of the head suspension can be flush with an outer surface of the stationary member opposite to an inner surface which is mounted on the carriage arm.
Further, to achieve the foregoing objects, according to another aspect of the present invention, there is provided a mechanism for producing a minute movement of a head, which is provided between a base portion of a head suspension having a head at an end portion thereof and an end portion of a carriage arm adapted to swing around a rotation shaft in a rocking type head actuator. This mechanism comprises a stationary member fixed at an end portion of the carriage arm, a moving member attached to the head suspension, a displacing member which is interposed between a predetermined free-end-side region surface of the stationary member and a predetermined free-end-side region surface of the moving member opposed to this stationary member and has a top surface adapted to be displaced with respect to a bottom surface thereof by applying a voltage in the direction of thickness thereof, and a sheet-like electrode member which is disposed on at least one of top and bottom surfaces of this displacing member and which consists of an insulating layer and conductive layers. The electrode member has a wire connecting portion connected to external wiring. This wire connecting portion is folded along a side surface of the carriage arm.
According to the present invention, in a head actuator of a magnetic disk device, a mechanism for producing a minute movement of the head can have a structure suitable for accessing disks mounted at small intervals. Moreover, the cost of the disk device can be reduced by simplifying the wiring for driving the mechanism for producing a minute movement of the head, and the wiring for connecting the head suspension to the ground.